Unable to delete child table follow by parent with Transaction

No problem to delete on delete1 action, but encounter 'The Head cannot be deleted because it is being used by Line.' error on delete2 action(with transaction).

/*
CREATE TABLE head
(   head_id VARCHAR NOT NULL PRIMARY KEY,
    name VARCHAR
);
*/
use Phalcon\Mvc\Model,
    Phalcon\Db\Column,
    Phalcon\Mvc\Model\MetaData;

class Head extends Phalcon\Mvc\Model {

    public function initialize() {
        $this->setSource('head');

        $this->hasMany('head_id', 'Line', 'head_id', array(
            'foreignKey' => array('message' => 'The Head cannot be deleted because it is being used by Line.')
        ));
    }

}

/*
CREATE TABLE line
(   line_id VARCHAR NOT NULL PRIMARY KEY,
    name VARCHAR,
    head_id VARCHAR NOT NULL REFERENCES head (head_id)
);
*/
use Phalcon\Mvc\Model,
    Phalcon\Db\Column,
    Phalcon\Mvc\Model\MetaData;

class Line extends Phalcon\Mvc\Model {

    public function initialize() {
        $this->setSource('line');

        $this->belongsTo('head_id', 'Head', 'head_id', array(
            'foreignKey' => array('message' => 'The Head does not exist.')
        ));
    }

}

class TestController extends Phalcon\Mvc\Controller {

    public function indexAction() {

    }

    public function createAction() {
        $head = new Head();
        $head->head_id = 'h1';
        $head->name = 'head 1';

        $line = new Line();
        $line->line_id = 'l1';
        $line->name = 'line 1';

        $head->line = $line;

        if (!$head->save()) {
            foreach ($head->getMessages() as $message) {
                echo $message . '<br/>';
            }
        }
    }

    public function delete1Action() {
        //$manager = new Phalcon\Mvc\Model\Transaction\Manager();
        //$transaction = $manager->get();

        $line = Line::findFirst(array(
                    'line_id = :line_id:',
                    'bind' => array('line_id' => 'l1')
        ));

        //$line->setTransaction($transaction);

        $head = $line->head;
        //$head->setTransaction($transaction);

        if (!$line->delete()) {
            try {
                //$transaction->rollback();
            } catch (Exception $e) {

            }

            foreach ($line->getMessages() as $message)
                echo $message . '<br/>';

            return;
        }

        if (!$head->delete()) {
            try {
                //$transaction->rollback();
            } catch (Exception $e) {

            }

            foreach ($head->getMessages() as $message)
                echo $message . '<br/>';

            return;
        }

        //$transaction->commit();
    }

    public function delete2Action() {
        $manager = new Phalcon\Mvc\Model\Transaction\Manager();
        $transaction = $manager->get();

        $line = Line::findFirst(array(
                    'line_id = :line_id:',
                    'bind' => array('line_id' => 'l1')
        ));

        $line->setTransaction($transaction);

        $head = $line->head;
        $head->setTransaction($transaction);

        if (!$line->delete()) {
            try {
                //$transaction->rollback();
            } catch (Exception $e) {

            }

            foreach ($line->getMessages() as $message)
                echo $message . '<br/>';

            return;
        }

        if (!$head->delete()) {
            try {
                $transaction->rollback();
            } catch (Exception $e) {

            }

            foreach ($head->getMessages() as $message)
                echo $message . '<br/>';

            return;
        }

        $transaction->commit();
    }

}